Identification of single transiently opening ("A-type") K channels in guinea-pig colonic myocytes

• Published in: Pflügers Archiv Vol. 429; no. 2; pp. 160 - 164
• Main Authors: Vogalis, F, Lang, R J
• Format: Journal Article
• Language: English
• Published: Germany 01-12-1994
• Subjects: 4-Aminopyridine - antagonists & inhibitors; Animals; Colon - physiology; Guinea Pigs; Membrane Potentials; Muscle, Smooth - physiology; Patch-Clamp Techniques; Potassium Channels - physiology
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/BF00374307

Two K+ channel populations were identified in depolarized cell-attached membrane patches of myocytes freshly dispersed from the circular smooth muscle of guinea-pig proximal colon. First, a large-conductance (150 pS) Ca(2+)-activated K+ channel which was non-inactivating and sensitive to blockade by tetraethylammonium (TEA, 0.5-5 mM); and second, a smaller conductance K+ channel which opened and closed within 100 ms, was insensitive to TEA (0.5-5 mM), but was blocked by 5 mM 4-aminopyridine (4-AP) or maintained depolarization, and which had a unitary conductance of 12-13 pS. The averaged time course of these smaller conductance K+ channels closely resembled the time course of the 4-AP-sensitive, Ca(2+)-insensitive transient outward K+ current recorded in the whole-cell recording mode.